The laundry process generally has several benefits for fabric, the most common being to remove dirt and stains from the fabric during the wash cycle and to soften the fabric during the rinse cycle. However, there are numerous disadvantages associated with repeated use of conventional laundry treatment compositions and/or the actual laundry process; one of these being a fairly harsh treatment of fabric in the laundry process causing fabric to lose its shape.
One aspect of the present invention is therefore directed towards maintaining the new appearance of fabric, that is to give better return (after being stretched) to the articles original shape (shape retention).
The creasing of fabrics is also an almost inevitable consequence of cleaning fabrics, such as in a domestic laundering process. Fabrics also become creased in wear. Creasing can be a particular problem for fabrics, which contain cellulosic fibres such as cotton, because the creasing is often difficult to remove. Generally, the creases, which are developed in a fabric during laundering, are removed by ironing. However, because ironing is seen as a time consuming chore, there is an increasing trend for fabrics to be designed such that the need for ironing is reduced and/or the effort required for ironing is lower.
Compositions for reducing the wrinkling of fabric are described in WO 96/15309 and WO 96/15310. The compositions contain a silicone and a film-forming polymer and it appears that it is the lubricating effect of the silicone, which is responsible for their anti-wrinkle properties. This conclusion is supported by the fact that a wide variety of polymers is mentioned as being suitable for use in the compositions.
Industrial treatments of fabrics to reduce their tendency to crease are known. JP-A-04-50234 describes a textile treatment in which the crease resistance of a plain weave cotton fabric is increased by applying a so-called “shape memory resin” to the fabric. However, this document teaches that the resin is applied to the fabric at a relatively high amount of 10% by weight on weight of fabric and it is not clear how this level of resin affects other properties of the fabric. Furthermore, treatment of the fabric with the resins is followed by a step of drying at 80° C. and the shape memory function is described as being heat-sensitive, with deformations at normal temperatures being restored to the original shape on heating at a specific temperature.
A relationship between polymer elastic properties and the ability to impart improved wrinkle recovery to cotton fabric is described by Rawls et al in Journal of Applied Polymer Science, vol. 15, pages 341–349 (1971). A variety of different elastomers was applied to fabric and, particularly in the few cases where thermoplastic elastomers were used, the polymers were applied to the fabric at the relatively high levels of 4% and above. There is no indication that any benefit would be obtained in applying polymers to the fabric at lower levels and no suggestion as to practical applications of the technique.
Durable press treatments (a.k.a. “permanent” press treatments) in the textile industry are well known. In the 1960's, it was known to use polycarboxylic acids for permanent press treatment of textiles. Generally, cellulose fibre can be cross-linked and esterified with polycarboxylic acids, particularly those with two or more carboxylic acid groups. Esterification is achieved upon heating the treated cellulose fibres such as by ironing or other forms of heat pressing. Curing catalysts, such as phosphorous containing salts, are also known to serve to aid cross-linking. Examples of US patents relating to durable press finishing of cotton textile with polycarboxylic acids include: U.S. Pat. No. 4,820,307 (Welch et al.), U.S. Pat. No. 4,795,209 (Welch et al.) and U.S. Pat. No. 5,221,285 (Andrews et al,). The contents of these patents are incorporated by reference. Compounds such as formaldehyde-based polymers, DMDHEU (dimethylol dihydroxy ethylene urea) and BTCA (1,2,3,4-butane tetracarboxylic acid) may be used as the cross-linking agent. However, these treatments have the disadvantage of reducing the tensile strength of the fabrics. Also, the high cure temperatures and long cure times required for such treatment have effectively prevented the use of such treatments in a domestic laundry environment.
It has now been discovered that the cure temperature and time of such processing can be reduced down to that of a domestic ironing step by using a higher level of curing catalyst in the treatment composition. Also, by incorporating a thermoplastic elastomer into the composition, the disadvantage of reducing the tensile strength of the fabric is overcome and the elasticity and resistance to creasing/wrinkling of the fabric is surprisingly improved.
The present invention therefore aims to reduce the tendency for fabrics to become wrinkled or creased.
The invention further aims to reduce the deleterious effects on elasticity and tensile strength of fabrics, which some conventional anti-wrinkle treatments impart. The invention may also provide a degree of shape retention in the fabric.
In addition, the invention aims to provide a fabric treatment which can be utilised in an industrial or domestic environment.